The immediate cause is a decrease or lack of GnRH pulses. This may occur idiopathic, or as a result of stress or lack of caloric support. Eating disorders may lead to hypothalamic-pituitary dysfunction. Measurements of FSH and/or LH tend to show low or undetectable values, and sex hormones produced by the gonads show low levels as well.
Hyperprolactinemia as well as a number of lesions in the hypothalamic or pituitary area may also lead to hypogonadotropic hypogonadism and need to be excluded before the diagnosis of hypothalamic-pituitary dysfunction can be made.